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Can fighter jet weapons be fired by ground personnel?
Does it makes sense for fighter pilots to have a ground personnel be connected to the aircraft and be able to fire weapons to help/offload work specially on stressful/critical situations?
(You know is not the same being inside an airplane when you know you could go down if you get hit vs someone sitting at the desk miles away with less stress to make decisions)
I don't know if this already exists but I see these advanced fighter jets like the F-35 with so much technology and features but had never heard about something like that and I thought if this already existed or it just doesn't make sense to help the pilots in this way.

It is probably also worth noting that the 'unload pilot' part is already done, with data links providing various forms of 'fly to here' capability reducing pilot brain space needed for navigation, and things like laser designators and various HUD tools simplifying getting weapons onto target.
In fact for many weapon types the main pilot responsibility is the act of firing itself, with much design effort going into removing other steps or effort.
Purely from the practical point of view having people off the aircraft able to release weapons has some side effects:

Simple safety issue from pilot being startled by unexpected weapon launch leading to crash or even ejecting thinking they have been hit. Off board firer also needs to know and understand what attitude/speeds are safe for firing.
Makes various forms of hacking both more possible and more valuable. Detecting hacked system much harder with no human in loop going 'hey this aim point I got sent is odd'. Even hypothetical risk of a hack may impose limitations or restrictions that make system less useful (eg flying with key systems powered off, then needing 10 minutes to come online when they are suddenly required).
Room for many more bugs/design issues that MUST get fixed, rather than just being a mild inconvenience. A 1% chance that a target uplink corrupts the co-ordinates (eg due jamming) is bad but still usable with pilot there to sanity check, a remote fire system would need to solve part of the two generals problem to confirm target data at aircraft is in fact correct.
Systems need to be added to prevent ground firing etc, potentially preventing pilot using weapons when they actually need them if they fail or are misconfigured.
A straight 'shoot this' target uplink can be one way to aircraft, a properly configured remote fire system should be two way to allow authentication and confirmation of target, meaning aircraft operating over enemy territory is transmitting, vulnerable both to jamming and detection (or even engagement by RF homing weapons).
Possibly a plus depending on how you see things but splits the decision to commit murder between the pilot and the remote person pressing the red button.

Very good points on the side effects.

If you need two people to operate a combat aircraft in stressful situations, which combat by definition is, you put two people inside that aircraft. The F-14, the F-15E, the Su-30, and many other reasonably modern fighters are two-seaters, with a weapon systems officer doing just that. So are virtually all bombers and larger aircraft.
If you were to give control over weapons to people on the ground, you might as well not put a pilot inside at all. Space missions were completely unmanned as early as the 1960s. Drones clearly are controlled from the ground, but that's presumably not the spirit of your question.
In the F-35's case, its advanced technology is largely there to reduce crew workload. It's not very fast, it's not very maneuverable, it's not the F-22, but it's got more smart anything than anything out there. Its pilot experience has been criticized for data overload, though, so it might be overdoing the smart thing.
Complex avionics and smart weapons indeed take a lot of work to operate. To ease that workload, most modern fighters support some form of a data transfer cartridge, which allows waypoints, parameters, and target coordinates to be programmed on the ground. That's essentially what you propose - just done in advance.
The pilot or the WSO still needs to be the one pushing the final button. They might be under more stress, but they also are the one in the situation. In most cases, engaging a presumed hostile requires confirmation from the command first.
Once the fighting has started... stress has a purpose, it helps one make snap decisions. Or maybe our culture just finds it more acceptable when these decisions are made by the person in danger. Either way, that's the way it's done for manned aircraft.
There's also been accidents where a weapon was fired on the ground - it's not supposed to happen.
The cannon was fired by ground personnel, with destructive results.
Nowhere near as devastating as when it happens to a rocket.
That wasn't meant to happen, the safeties just failed.
So generally unintended launch is a bigger concern than a pilot's failure to launch.

oops, totally forgot 2 seat aircrafts, makes sense. The F-16 article you mentioned looks like it was more something like a malfunction/accident and not an actual firing by someone pushing a button from outside the aircraft. Also the fb post linked from that site flags it as false information: https://www.facebook.com/Scramblemagazine/posts/2441220252571161?ref=embed_post

@Gabe Yes, these are both accidents. But they do answer the question ;) They can, but it's desirable that they aren't.

As for Facebook, even its "fact-checking" can't be trusted. Belgian Air Force itself confirmed the event. The only part of the article BAF disputes is that "it was a stupid mistake" - they claim they work hard, get tired, mistakes happen, and there's nothing stupid about it. Sure, but that's... not a denial.

@Therac - For an F-16 gun to fire on the ground other than intended, multiple things needed to go wrong. Some mechanical, some human.

@Therac are you saying that this an actual feature of the F-16? Are you saying that someone on the ground can fire a weapon on an F-16 while in the air? Can you reference any other information that that is in fact possible other than that event article? (from what i red it sounds that this was a malfunction that caused this not that it is a functionality and that someone just pushed the button by accident)

@Gabe No, the gun isn't supposed to fire while on the ground. There are multiple safeties.. It's possible to bypass them and shoot, however.

Currently, no, munitions in a manned jet cannot be fired by a person on the ground.
In the unmanned MQ-9 Reaper, yes.
As the B-21 Raider platform matures, that will be optionally manned, and weapons deployed by crew on the ground.


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Where are the oxygen masks for the flight attendants located?
On a typical airliner, while seated in their jump seat, where is the oxygen mask located for the flight attendants? (an image would be appreciated)

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Can this plane make it to an airport after dual engine failure?
If you are flying to the most remote airport(according to simple flying most remote airport is Mataveri International Airport), while flying on a typical airliner with normal weather, in the event of a dual engine failure right at the middle point of the flight, would you be able to glide to the destination airport or origin airport for that matter?
UPDATE:
After answer from @Mike Sowsun saying you only have roughly about 100 miles to glide, I went to FR24 to the Gulf Of Mexico to find a shorter , simpler, less extreme flight and found this United flight(Houston->Belize) right in the middle of the Gulf of Mexico. In this case, if this airplane loses both engines at this point, does this means is game over?

Screenshot taken on 2024-04-09
(I measured the distance on google maps from this point to all land points and is definitely more than 100 miles)

The whole point of ETOPS is, you plan to be able to lose 1 engine & get to a suitable airport within a specified time (sometimes 60 minutes, sometimes 180, depending on the specific certification).  The possibility of losing the 2nd engine in that timeframe is in the category of "accepted risk" -- it's sufficiently unlikely (i.e. 99.9999999% of all flights, "nine nines," won't have it happen) that we're willing to live with the not-quite-zero possibility. There is no perfect safety in the world, but 1-in-a-billion is considered acceptable odds.

I know a dual failure is rare, but actually happened recently at Naples: https://www.youtube.com/watch?v=64aLtnT5E8s

Not all aircraft are ETOPS certified, and some things (bad fuel, running out of fuel) can demolish the assumption of independent failures.  ETOPS programs are set up very carefully to avoid those sorts of non-independent failures.

@RalphJ I'm not  expert on ETOPS, but does ETOPS certified provides conditions for fueling an  aircraft from two different sources in case of fuel contamination scenario? (the same way pilot and copilot eat different meals)

Not necessarily, but quality checks on the fuel could be more frequent & strict. Airline fueling is a very controlled, consistent process, compared to what GA & bizjets may experience.

Can you describe what "Normal weather conditions" are because from place to place what is considered "Normal weather" Varies quite a lot

@JordanStephan well, if you want let's take the exact weather they are flying. You can go to FR24 and you are going to find an aircraft passing right at the middle of the gulf of mexico every day, just take the current weather at that time.

I wouldn't say "game over": they can still ditch and wait for rescue.

@sophit conversely making it to an airport doesn’t guarantee a successful landing

@Frog yeah, that's true, but statistically you have more chances to have a successful landing at an airport than in the middle of the ocean.

No, if you were in the middle of a flight, you would not be able to glide to an airport. A typical airliner, at typical cruise altitudes, would have a maximum glide distance of about only 100 miles. (very rough estimate)
There have been at least two cases where a passenger airliner has experienced total engine failure and glided to a safe landing.
Gimli Glider
Air Transat Flight 236

oh wow didn't knew the glide distance was that small. Well, correction, thinking about it actually is not that bad.

A typical airliner has the glide ratio of a low end glider -- typically 20:1.  That means from an altitude of 10 km, you'd get a maximum of about 200 km glide distance.  In practice, you get less than that due to maneuvering, weather, RAT deployment, and having to lower landing gear well ahead to be sure you have it down in time.

@ZeissIkon shame on the pilot who falls short of the airport because of lowering the gear and flaps! I hope that the airline pilots are well-enough trained not to configure for landing until the field is made. (Of course, the number one reason for glider crashes is the plane coming up short, so if even glider pilots get it wrong frequently, I'm not sure what that says about jetliner pilots).

Don't forget the gear takes longer to come down when you don't have a running turbine or APU to power it (most airliners don't have a "gravity" extend mode, AFAIK).  Pilots who don't intend to belly land might have to start lowering gear a fair way out to be sure it has time to lock.  The decision which strip to land on is where you;d come up short, anyway -- as almost happened with the Gimli Glider.

Don't forget Sully, and this is the list of airline flights that required gliding in the last 80 years.

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Can a smaller wing area smooth the ride during turbulence?
Amid the recent incident of Singapore Airlines flight 321, leaving one dead after a severe turbulence, I ask myself if having an aircraft with smaller total area, there is less turbulent air that touches the aircraft hence the less it can 'push' the aircraft which would translate in smoother ride.
In other words, if you make an airliner essentially a 'flying fuselage'/rocket, can we  say that the ride would be smoother than an normal airliner flying at the same speed, alt, weight, etc, ... correct?
I was thinking of a similar real life example and thought of the F-14 Tomcat and I ask if anybody knows if this aircraft experienced less bumps when the wings were swept while flying trough turbulence?

(source)
If that is the case then, would building an aircraft with more retractable areas on the wing(like the flaps are) and combining maybe with something like the F-14 swept wings design be a posible solution to lessen the effect of unexpected severe turbulence?
Maybe something like this:

I don't have anything to back it up, but I have heard aircraft with higher wing loading are less affected by turbulence. Is that because they are closer to the critical angle of attack, and if an area of the wing hits an updraft, that area just stalls instead of pushing the plane up? Is it just because there might be less wing area out there compared to a lower wing loading (measured per area) plane, with larger wings that catch the updraft more?

Smaller wings need more airspeed to make the same lift, so a fair comparison may be tricky.  A wide wing pushes down a big parcel of air.  A tiny one pushes down a thinner but "longer" (because flying faster) one.  Which one encounters less air mass?

There isn't any increase in turbulence in "our world climate" today. These events have happened in the past and will continue to happen. The news item about some study that projects an increase of CAT severity due to "climate change" is based on a software model. Software models can barely manage predictions beyond 24 hours. This is research chasing funding dollars. Weather is about temperature differentials. If the climate is warming, differentials are reduced as the poles warm more than the equator. A shallower equator to pole temperature gradient means less severe weather.

@JohnK Thanks, I've removed that part to avoid derailing this post and so that we can focus on the main question, which is about aerodynamics.

The F-14  does not illustrate your smaller wing area question. The swept wing has much the same area as the unswept wing but a much narrower span, so either your title or illustration aircraft needs to change.

@JohnK  That's a lot of opinion there, without any citation. Weather is actually caused by ENERGY differentials, not just temp, and is demonstrably getting more extreme.

@Pilothead for the purpose of a gust on the total area of the vertical component, it does change, see my comment to @ sophit answer who has a similar comment to yours.

@MikeB That's a lot of opinion there, without any citation lol. The evidence of weather getting more extreme is software models, which can't model clouds (cloud dynamics are too complex to model and so are entered to the GCMs as "parameters".  Then the parameters are "tuned", the values secret, to achieve a correlation.) See AR5, WG1, Ch9, Page 749. This is not science. So when I see a hysterical article predicting oh-dear-oh-my worsening of CAT events, and check into it, and discover it's from a study that is based on a software model, the BS-O-Meter dials up to 11.

Gust analysis is a quite complex matter, so complex that big airplane companies have dedicated departments only for this topic.
Anyway an easy way to understand how a gust influences the flight behaviour of an airplane is by considering a so-called "step" (or "sharp-edge") vertical gust (figure (a) in the following picture - source):

Before encountering the gust, the wing was developing a lift that, as usual, is expressed by:
$$L=½ \rho V^2 S C_L$$
As a good approximation we can consider $C_L$ as being linearly dependent on the AoA $\alpha$ and therefore:
$$L=½ \rho V^2 S k \alpha$$
Upon encountering the gust, the lift $L$ changes both due to the increase in the AoA and in the total speed (plot source):

$$V \rightarrow \sqrt{V^2 + U^2}$$
$$\alpha \rightarrow \alpha + \frac{U}{V}$$
where $\frac{U}{V}$ is an approximation valid when $U$ is much smaller than $V$, as it is usually the case. Substituting we get:
$$L=½ \rho (V^2 + U^2) S k (\alpha+ U/V)$$
Since we are interested only in how much the lift has changed due to the gust, we subtract this latter equation for $L$ from the former getting, after some simplifications:
$$\Delta L = ½ \rho S k (VU + U^2 \alpha)$$
Now, in order to reduce this $\Delta L$, we can reduce:

$S$ - wing surface - and/or
$k$ - slope of the lift curve - and\or
$V$ - flying speed.

Obviously the wing surface cannot be changed in flight (except when flaps are deployed but that's another story) so the only way to counteract a gust is by:

reducing speed - this is normally done by the pilot - and/or
decreasing the slope of the lift curve - this is normally done by some automated gust-alleviation system using the spoilers or other control surfaces to change the slope; yes, changing the wing geometry as on the F-14 can be a way to change the slope of the lift curve since wings with lower aspect ratio tend to have lower slope of the lift; anyway this is not going to work since gust is, by definition, something relatively sudden while changing the wing geometry on the F-14 takes some seconds; this is why gust-releaving system are automated system whose sensors are placed as forward as possible on the airplane in order to give the system enough time to elaborate the signals and move the control surfaces on the wing.

P.S.: please note that the wing surface of the F-14 does not change, the geometry of the wing does.

Though the wing itself on the F-14 doesn't change, when it is swept there is slightly less area that the gust can touch on the vertical component (figure (a) of you answer). You can see this clearly on the picture of the original question post and notice there is a black stain/discoloration on the fuselage which is the area of the wing that overlaps with the fuselage which I would say is about 10% of the total wing area. This in turn makes the whole aircraft to have at least 10% less of total area on the vertical component (figure (a) of you answer).

btw, I wasn't thinking of using the F-14 wing swept mechanism as a way to react to the prediction of a gust ahead. I was thinking of it as a permanent/fixed solution during cruise flight (the wings would be swept during the whole cruise phase, there is no need to install any gust prediction sensors)

Then yes, it might be an option. Obviously you have to take into account also the cons like higher structural weight, shift of the aerodynamic centre, ...

The F-14 with highly swept wings is less affected by air loads like turbulence than at low sweep, as shown by maximum allowed airspeed. Max speeds (TMN is true mach number) are higher when wing sweep is higher. From the flight manual:

So the answer to your second question is yes, variable wing sweep would reduce felt turbulence, but this is expensive and would cost more than it was worth.

Excellent question presentation, because this one was originally designed in a similar manner as the F-14.
Not only faster, but higher, in the Stratosphere, where turbulence is less common.
The effect of turbulence on an aircraft is a function of wind speed, density, and cross section area to the change in wind direction.
Higher, faster, with smaller wings all minimize turbulence effects.
Fuel costs ended the anticipated transition to supersonic passenger flight in the 1970s, leaving us with slower, more economical designs with lower wing loading, with the exception of the Concorde.
Because the slower aircraft are more economical, efforts may focus on improved detection and/or forecast of turbulence.

Higher speed amplifies turbulence loading. Vb is a maximum.

@Pilothead that would be faster in the same configuration at the same altitude.  Higher and faster would mean same IAS in thinner air, lessening the effect of an up or down draft at the same velocity.  Good point about Vb however.

A better example would be the B-1. It began as a supersonic, high-flying bomber (B-1A) but was soon converted to a subsonic, terrain-following intruder (B-1B) with limited stealthing to increase survivability in a high-intensity conflict. The variable sweep was a big help in this conversion, as the swept-back wing gave the best possible ride qualities at low level due to the reduction in the lift curve slope from the high sweep angle.
A smaller wing will help again to reduce buffet loads. If we consider a vertical gust and assume that its additional wind speed will increase angle of attack by a given amount, this amount will become relatively smaller for a smaller wing flying at a higher lift coefficient.


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Should I switch the transponder to STBY or not while changing codes?
I´m now reading Bob Gardner’s book “Say again, please” and there is this instruction on page 54:

Do not turn the transponder function switch to STBY while changing codes.

What is the reason for this? I’m a PPL student and my instructor told me the opposite.

The FAA started advocating not selecting standby for code changes after it was found that more often than one would expect, the transponder doesn't always come back on after standby.  Seems they uncovered a number of switch failures.
I figure that someone decided that for TCAS it was better to have a transponder squawking any code than not squawking.  But that is my own conjecture.
So for quite a few years the guidance has been to not turn to standby when selecting codes.
I have had the folks at Flight Safety lecture me after sim sessions, with pretty much the same story.
So I now teach students to just switch the codes, and not standby the transponder.  And I suggest caution when dialing through "7xxx" although controllers I have talked to say it's not a big deal.
So the idea is to keep the transponder squawking, even though numbers are being changed.  There is continuity in that they will continue to have returns while you are playing with the knobs. And if you ever have a switch failure, it will likely be on the ground.
Addendum: Also, with ADS-B, one is supposed to keep the transponder on at all times, when on the airport surface in a movement area. So I can see that the philosophy of managing the standby position will continue to change.
Also note that Bob Gardner's book was from the mid-1990's and things change. Both the transponder technology, the technology, such as ADS-B, TCAS (which also relies on transponders, as well as processing algorithms, which decide how to display transitioning codes.

Also, it is probably more likely for it to be "pilot error" than "switch failure" when the transponder doesn't come back on after setting the code....

Modern electronically controlled transponders have a delay that waits until a few seconds after dialing stops before committing the change. And a lot of them are keypad entry now, which avoids the problem too.

For a while I would fly a plane daily which would not do the 0400 bit, and of course the local TRACON assigned 0400 bit codes. The unit would go to the shop, get certified and then the switch(i assume) would get spotty. I would negotiate another code with ATC.  The only people who were really annoyed were the NYC TRACON folks.  Then again, at one time, I flew equipment which had two digit transponders.  Yep, 12 for VFR.

Good answer. I'd like to add that the transponder interrogation rate for terminal and enroute radars is quite low (5-10 seconds). As such, if you make the code change in less than 5 seconds, the radar will receive at most one, and quite possibly zero, transient codes. I don't suggest rushing through the code change, but it's worth knowing that ATC is not seeing every single transient code you cycle through as you're twisting the knobs.

@TypeIA Also, ATC will be very aware of the fact that they've just assigned you a new code and are expecting to see it change.  Other than emergencies, it should never be a surprise to ATC when your transponder code changes.

Someone told me a few years ago that enroute radar looked for three interrogations before triggering alarms.  I don't believe it, but this person should have known.  I do know that I have seen people switching codes with TCAS.

So the only reason to switch it to standby when dialing a new code is too avoid broadcasting a false code which may be send out by transponder „in the middle” of dialing a new code?

The AIM implies that you should leave the transponder on ALT when changing codes—since if you are in standby you won’t be transmitting:

4−1−20. Transponder Operation
e. Code Changes

When making routine code changes, pilots should avoid inadvertent selection of Codes 7500, 7600 or 7700 thereby causing momentary false
  alarms at automated ground facilities. For example, when switching
  from Code 2700 to Code 7200, switch first to 2200 then to 7200, NOT to
  7700 and then 7200. This procedure applies to nondiscrete Code 7500
  and all discrete codes in the 7600 and 7700 series (i.e., 7600−7677,
  7700−7777) which will trigger special indicators in automated
  facilities. Only nondiscrete Code 7500 will be decoded as the hijack
  code.


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What are dimensions of the B-17 propellers?
I'm curious about the aerodynamics of the Boeing B-17 propeller, as the proportions looks perfect for a project I'm working up. Does anyone out there know where to find the specs/dimensions/models for the B-17 prop?

According to the maintenance manuals from here about halfway down the page (part 1 page 3) the B-17 was equipped with:

PROPELLER.

Type: Three-bladed, hydromatic, WEE50-473 or 505,
  full feathering.
  Mfgr.: Hamilton Standard.
  Hub: 23E50-473.
  Blade: 6477A-6.
  Diam.: 11 ft. 7 in.

Part two of the manual has all the installation and setup instructions instructions if you are looking for those as well.
Hamilton Standard seems to have been acquired by (or turned into) UTC Aerospace which appears to still make propellers. You may want to reach out to them as they may have more info on hand. There are quite a few B-17's lurking around and there may even be one near you that you can go take a look at and possibly even measure.


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Why Didn't the USSR Build An X-15?
In the history of aerospace engineering in the United States, the X-15 is lauded as a critical and necessary step on the path to manned spaceflight. Throttle-able chemical rocket propulsion systems, reaction controls, and pressurized flight suits were all major design features of the X-15 that eventually found their way into future successful spacecraft.
Given the obvious resources the USSR put into the space race and their numerous successful missions, why did they never build a hypersonic space-plane akin to the X-15?

As a rule of thumb, be slightly skeptical of the merits of any device when they are being loudly praised by the nation that built it in the first place. Doubly so for Cold War toys.

@AEheresupportsMonica Fair enough. However, we learned so much about aerodynamic heating and atmospheric reentry from that program, it's amazing to me that the Soviets managed to completely skip this step on the path to space

Given the technological components you mention, if you have no answer here you may consider asking on space.SE.

I'm voting to close this question as off-topic for aviation, it's a question for Space.SE

It's a spaceplane, arguably it belongs in both

I disagree with the close vote, this thing barely reached space. Not trying to discredit the engineering behind it, though, but the fact that most of its flight was in atmosphere qualifies it for this site in my opinion

It's asking about benefits to the US space program, and why the Soviets didn't build one to benefit their space program. I'm active on Space.SE, to me it's definitely a better fit there, however I'll answer and if it moves, it moves.

@GdD that's fair, the space race angle is something that site might cover better. Maybe just ask it on both?

That's generally frowned upon @AEheresupportsMonica

@GdD I've heard as much, but SE has no qualms with overlapping sites (space/aviation/engineering/electrical engineering/robotics), so it feels like an odd procedural hurdle.

As a frequenter of Space.SE, a fair amount of the X-15 is still a plane. Considering that the X-15 also needs a carrier aircraft to operate, this really is a better question here. See the X-15 excerpt on Space.SE

Why did the US build the X-15 while Russia was busy landing on Venus and otherwise utterly winning the space race?  Probably to spy on Russia because we were losing.

Was there an equivalent Russian program to the U-2/SR-71 spy planes? – Reddit "The soviet union did order a copy of the U2, to be made - the Beriev S-13. It never did fly. By the time it was cancelled, in 1962, the Zenit series of spy satellites were in operation."

iirc, at some point the CCCP focused on defense-ranged bombers instead of being able to bomb the US with planes, as their ICBMs were up to the task. Might as well just steal some plans for the space shuttle because these type of things are no longer needed for reconnaissance.

This article is closer to my own feelings about the X-15, but who knows if it truly was a necessary step in aerospace research
https://www.airspacemag.com/history-of-flight/why-we-miss-the-x-15-22716858/?all

@AEheresupportsMonica if it "barely reached space" then it did in fact reach space, making it by definition a spaceplane.  You may not like it, but that's what concrete definitions are for.  If your team wins the game by one point, the opposing team may complain that your team "barely won", but your team still did, in fact, win.

@gillonba I think you are reading way too much into my comment, I was not trying to discredit the X-15, as evidenced by my next sentence.

https://en.wikipedia.org/wiki/Burya is somewhat similar in concept, although unabashedly a weapons delivery system.

I like the X-15, it was certainly an amazing airplane, but the truth is there were few benefits to the space program from the X-15.  It was far from a critical or necessary step:

The Mercury space suit was a direct derivative of the BF Goodrich Navy Mark IV, which had been in use for years. It wasn't developed for the X-15
The rockets used in the space program were completely different from the X-15. They were orders of magnitude stronger for one thing, used different fuels and completely different designs. Throttle-able rocket propulsion systems weren't new
The X-15 thermal protection system was of no use to the space program, which had to deal with far higher temperatures

There were some benefits:

It was a good source of astronauts: several pilot from the program went on to the NASA programs, including Neil Armstrong
Data from the X-15 missions were used in the X-20 Dyna Soar spaceplane which never flew, but it eventually morphed into the space shuttle

As to why didn't the Soviets make one, they didn't need it. Their manned space program built off of their ICBM development efforts which were successful. If the US hadn't built the X-15 the manned space program would most likely never gone the space shuttle route, but that wouldn't have been any sort of deal breaker.

Do we know how the USSR learned that using blunter bodies is better for reducing stagnation point heat transfer?

I don't @BrysonS. A lot of Soviet space development is still hidden. It's very possible they learned it from the US Government's own published materials, pictures of the X-15 and subsequent spacecraft designs.

@BrysonS. iirc detached shock wave location can be predicted nicely from the theory, I don't think there was a need for a prototype except to validate the model.

@GdD: So, I used my language joker and googled a bit. Russian Wikipedia (duh) says the shape of Souz was chosen "by March 1963", but lamets that it has not so good aerodynamic quality that leads to overheating. It is stable, however. In http://www.buran.ru/htm/cliper02.htm they just state that the shape was derived from the re-entry ability. There is some scan under http://akf.bmstu.ru/images/%D0%93%D1%80%D0%B0%D1%87%D0%B5%D0%B2%D0%B0%20%D0%9A%D0%9C%20%D0%96%D1%83%D1%80%D0%B0%D0%B2%D0%BB%D1%91%D0%B2%20%D0%95%D0%98.pdf, they list various shapes in "Рис. 3". Hope that helps.

Thanks @OlegLobachev.

'extremely successful' : Soviet space program, Notable firsts

One thing I read was that the X-15 was largely an attempt by the USAF to stay relevant in the space program after NASA was established based on technology related mostly to Army and Navy rockets. So classical US military inter-service rivalry.

The USAF had their own manned space program for awhile @jwenting, with some big plans.

@GdD yes, they did. And it was under constant threat from the navy's and army's programs that were merged into NACA's program when NACA became NASA. X-15 was basically the last part of the AF's program to see the light of day as an independent (rather than tri-service or in conjunction with NASA) program.

I'll complement GdD's answer from a slightly different perspective.

In the history of aerospace engineering...

Wait, there is a problem right there. Due to various historical reasons, there was no aerospace industry in the USSR, at least the way it is known in the West. The very word "aerospace" was almost never used before the 90s. Aeronautics and space were much more separated than in the US. There were no companies that dealt with both the way Boeing or Lockheed did. (Though some were forcibly switched from aviation to space in the late 50s).
Space industry, especially at the early stages, had more affinity with artillery than with aviation. This involves not only the formal bureaucratic subordination, but the whole mentality, from design to testing. In this scheme of things, rocket designers wouldn't even think of building an 'aeroplane' (and X-15 is undeniably an aircraft) for testing. They would rather shoot a few more rockets. Especially given the preferrential supply of resources to the space industry.
There were some later attempts from the aeronautics industry to get involved, but none were remarkable (until, perhaps, Buran).

I think the MiG-105 program was also part of a conscious effort to incorporate lifting reentry into a space vehicle

Yes, and that's exactly what aviation could potentially contribute.

Well, Energia/Buran was remarkable by the fact that it only flew once (without a crew, at that).

@CalinCeteras that's in no small part because the USSR collapsed early in its test program, they simply ran out of money for more flights while several Buran craft were still under construction. It certainly showed promise.

The shape of the Buran was heavily based on space shuttle plans gained through espionage. They even copied the programmed after launch roll, even though they didn't know why. The Buran project was certainly a technical achievement, but there's a big bucket full of 'why?' that accompanies it.

@GdD do you have a source for that claim? I was interested in reading more about it but it seems hard to track down.

Which part @zymhan? The espionage part or something else?

There some great info on the Buran here: https://falsesteps.wordpress.com/tag/buran-shuttle/

Great question, but no, the X-15 was not a "critical and necessary step on the path to manned space flight" at all, it was used to test the feasibility of sustained and controlled
hypersonic flight of an aircraft at very high altitudes and speeds.  The X-15 was an extension of the X program, started in the 1940s, to continuously push the speed envelope of aircraft through the sound "barrier", and the thermal "barrier" beyond it.
Manned space flight, requiring rockets with much more thrust for far longer, simply is in another league, and was founded in the ICBM programs of both the US and USSR, which owed much of its foundation to the pioneering work of Goddard, and the development and scale up (including the all important turbo pump) of team von Braun.
Recovery systems from these flights were, and are, capsules.  It is rather dumb to haul an airplane into space when payload to orbit costs are measured in thousands of $ per pound.
The Space Shuttle was an awesome technology demonstrator, but never succeeded as a low cost replacement for ordinary rockets to move cargo to orbit, but remains a viable option as a means to return cargo and crew from orbit.
So, although the X-15 did reach the edge of space on some of its flights, and did use control thrusters, it was much more an airplane, and should be more than welcome as a subject for readers to enjoy on Aviation Stack Exchange.

There were three competing ways to space pursued in the US while in the USSR everything was centrally managed, so they followed only the way that Konstantin Tsiolkovsky had first proposed.
What were those three ways?

The US Navy used a home-grown team to develop a rocket at the Naval Research Laboratory. Their Vanguard rocket failed several times, however, before it worked as designed.
The US Army relied on a bunch of German engineers who had worked for the Wehrmacht artillery before 1945. Fittingly, they were housed in the Redstone arsenal grounds of Huntsville, Alabama. Their Juno rocket was used for the first US satellite launch after being placed in storage for almost a year so the Navy team could try first.
The US Air Force wanted to use a winged craft to get into space. For them, rockets were a temporary shortcut and several, rocket-powered test aircraft were developed in order to get closer to spaceflight. While also developing the Atlas rocket, the US Air Force in cooperation with NACA, later NASA, ordered several X-planes to test access to space and re-entry with a winged vehicle (X-2, X-15, X-17, X-20, X-23, X-24, X-30, X33, X-34, X-37, X-38, X-40, X-41 and the list goes on).

The planners in the USSR never planned something like the X-15. Also, when the X-15 flew, they saw no need to do something similar.

Opposed to this answers FIRST sentence - although soviet russia used to central manage everything .. their approach to space flight was a "competition of science bureaus" - at least 2 teams lead by Sergej Koroljov (OKB-1) vs Valentin Glushko / Vladimir Chelomei - both teams stood in heavy competition over the design principles - while the U.S .. the land of the free founded the NASA - ONE (large) organization hat should henceforth coordinate and manage ALL space activities. So  in hindsight NASA approach appears far more centrally managed

"NASA appears to be more centrally managed", until Wernher left the house.  The X-37B shuttle is in use today with the Air Force. Accuracy of capsule recovery seems to be improving.  Interestingly, the Gemini program did seem to have some thoughts about gliding in with a Rogallo wing, and included ejection seats with the capsule.

@eagle275: So one of the bureaus didn't follow Tsiolkovsky's approach? And I thought all were working on multi-stage rockets. So you say they weren't? And I thought that OKB 456 designed the rocket engines for Korolev and Chelomei tried to fill the void Korolev had left with his early death. The limited competition earlier was due to the trick of using Khrushchev's relatives which undermined central planning.

Well, to be fair, there was quite a bit of competition, sometimes fierce. But it was less of an open competition for who does better; rather, more of a competition for (bureaucratic) power: who convinces the authorities that his way is the 'right' one. Glushko, for one, was never happy making engines for Korolyov: earlier he was Korolyov's boss and struggled to accept being No.2; also he was a fan of UDMH while Korolyov pushed for LOX/Kerosene. The same in aviation. It's a more complicated picture than 'centrally managed'.

@Zeus: The point is that the plan focused on rockets and rocket-powered aircraft were not considered. Given the priority of rocket development, the bureaucracy tolerated some competition – in the end the USSR competed with the US as well.

not so much Ziolkowski's plan - but they competed over different rocket engines and fuel (cooled hydrogen/oxygen on Koroljows side, the others aimed for ICBM type rockets using solid fuels

Most of the X-15 data, like most NASA research studies are made available to the public.  Why spend millions of Rubles on a space plane testbed when you can examine the research data for free after the other guy spent the cash and built one?
And, apparently, as both the US and USSR space shuttles bear a VERY similar appearance to each other, it appears that both sides came to similar conclusions as to the best configuration for a space plane based on hypersonic research data from the X-15 program.

When was it made public?

I'm pretty sure this data was classified at least in the 50s and 60s.


text:
How to retrieve the thrust distribution over a blade using XROTOR?
What is the procedure for retrieving the thrust distribution over a propeller blade using XROTOR? I need the sectional (i.e., for each station) thrust coefficient values.
I was only able to retrieve the sectional lift and drag coefficients, but I would also need to know the inflow angles to get thrust, which I don't know how to get.


text:
Why does the F/A-18 have so many lift supplementing devices?
Leading edge devices, normal flaps, dog teeth, strakes. Why does the F/A-18 have so many lift assisting devices?

All those devices are aerodynamic devices.  Why do you think they are "lift supplementing?"  In my opinion all parts of a well designed airplane supplement lift, except for ballast and cargo.

@AnonymousPhysicist well the F/A-18 has more than other planes or fighter jets. The F-22 for example doesn’t have strakes.

@Wyatt the F-22 enjoys longer runways lol.

The leading edge strake extension is there to solve a handling qualities problem the airframe had at high angle of attack without it.
Not only does the aircraft need to fly at high speeds (which requires high wing loading -- bad for landing) and fly very slowly -- to land on an aircraft carrier (which would want low wing loading) -- it is also a fighter that needs to be able to maneuver aggressively.  This means high CLmax and preferably low drag at high lift during maneuvers.
The F22 has thrust vectoring to help with extreme maneuvers without aerodynamic aids.  It also has a stealth requirement that forces a much cleaner design.  You should compare the YF-17 to the YF-16 and then compare the F-18 to the aircraft it replaced (including the F-4).

F-22 is also not a carrier aircraft, which requirement distorts every design significantly.

True, but the YF-17 was not designed as a carrier aircraft either, but it has some (but not all) of the features asked about.  The F/A-18 A-C has a few more, the F/A-18-E,F gains even more.

Doesn't it also have foldable wings? That surely must have an impact too

It does -- and they certainly add weight.  The foldable wings can be done cleanly in terms of aerodynamics -- though the break in the leading edge of the E/F appears to be where the wing folds.

The F/A-18 Hornet was designed to take off and land on an aircraft carrier.  It also needed a very high maximum speed.
To fly very slow (to land on the deck) and very fast, different aircraft shapes are needed.  The designers wanted the plane to do both, so they designed it to change shape using big flaps.

Oh because of carrier landings? Makes sense, thanks.

"The designers wanted the plane to do both" without the weight + complexity (including cost) of swing wings.

@RonJohn It has folding wings for carrier operations.  I am not sure anyone has invented a plane with both folding and swinging wings.  That would be heavy.

Swing wings also reduce deck space.

The F-18 takes off from carriers, so it's wing surface is extensively modified to provide much lift surface as possible when carrying a full set of Stores.

So Point is... You place stores namely munitiions and payload racks on an F-18, that doesn't help well with aerodynamics. Then add single fuel tanks, and it already lowers top speed by a considerable degree. Put x4 AMRAAM missiles on each wing and Sidewinders. At this point its already flying nightmare.

@quietflyer: I think it's (or its??) just a matter of the automatic spellchecker being too invasive...


text:
Why did Southwest ask the FAA to ground their flights, rather than doing it themselves?
According to a tweet from the FAA, "Southwest Airlines requested the FAA pause the airline’s departures."
Southwest Airlines tweeted

We have had to implement a ground stop as a result of intermittent issues that were experienced, and we should hopefully be resuming our operation as soon as possible. I apologize for any inconvenience this may cause, but we'll be here for you if you need any assistance. -Katy

Why did Southwest Airlines have to ask the FAA to ground their flights? Couldn't they have done it themselves?

Pure Speculation: Do they gain some kind of insurance benefit if they "were canceled" instead of cancelling themselves?

If SWA wanted an immediate ground stop on additional departures, they would contact the Air Traffic Control System Command Center (ATCSCC) in Herndon, VA and request it. The ATCSCC would conference all enroute centers and inform them to ground stop all SWA departures due to company automation problems. The enroute centers will send out a message to all underlying facilities as well as the internal sectors to stop SWA departures with an expected update time. This whole process takes about 3 minutes and captures all aircraft irrespective of whether the aircraft are talking to dispatch.

So SWA doesn't have communication with all of their pilots, but ATCSCC does?

I don't know whether SWA can communicate with all of their aircraft all of the time. The ATCSCC can communicate with ATC facilities, not SWA pilots. It's the ATC facilities that will stop clearing aircraft for departure or rescind previously issued clearances.

@757toga I read that SWA had a problem with their computer network (a network firewall broke down). Could well be that they could not communicate to their aircraft at the time, or they could not find out which aircraft to contact because they lost access to ops data.

@user253751 maybe because SWA won't have communication with that plane, so allowing it to take off would be a violation of FAR 121.99 as described by 757toga?

I wouldn't read too much into a social media tweet; the space simply doesn't allow a person to explain in a way that captures the complexity or nuances of any relationship between a regulatory agency and a part 121 carrier.
In short, a carrier doesn't need FAA permission to cancel a flight.  There are slots reserved, so likely the tweet is a very brief paraphrasing of whatever notification process is used to inform the FAA of cancelled flights and "release" those booked slots to other carriers.

So the FAA cancellations would be to allow other airlines to take over the slots, not to allow Southwest to cancel the flights?

@Someone, I have never worked in airline dispatch or the FAA so I cannot answer with authority.  This is an educated guess based on some amount of random experience in aviation.  I would suggest not accepting my answer in case someone comes along with a better explanation of the process.  The main point is don't read too much into a single sentence "Tweet" as being authoritative and complete explanation.  It could be a social media intern told to put out something who didn't fully understand things.  People at the FAA are human too...  Maybe there is a more official press release?

@757, the verbiage used was in fact "ground stop." And remember of course that neither the FAA not Southwest uses tweets for operational purposes; they are only for after-the-fact public-information dissemination.

@randomhead Well, we've seen heads of state use tweets to run whole countries. The days of ATC happening over Twitter might not be too far ahead.

Lay-person typing: maybe it's to do with some aspects of regulation, insurance or other legal matters.
If your flight is cancelled, it most probably makes a difference e.g. with respect to compensation, whether it has been cancelled by the airline (they are simply not serving any routes) or whether is has been cancelled by the FAA (the airline has been temporarily banned from serving routes).

An operator cannot avoid compensatory responsibilities by asking FAA for grounding. They asked for it themselves, hence it would not fall under any force majeure. Asking for assistance from the FAA may have been the most convinient way of achieving fleetwide ground stop.


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Are rectangular fuselages more sensitive to winds than circular ones?
If you have an aircraft like the DHC6 twin otter or the SkyCourier (picture bellow which have a rectangular shape like fuselage) and then you have another aircraft with the exact same dimensions and fuselage total area but with the more common cylindrical shape, which aircraft would experience more turbulence or be more impacted by gusts/cross winds etc, the rectangular or the cylindrical fuselage?

So basically you asking "for the exact same projected side area (and the same distribution of projected side area), does the flat-sided fuselage create more sideforce, when there is a crosswind component in the relative wind, than the rounded one?"  A related question (or maybe a subset of the present question) would be would the airplane w/ the flat-sided fuselage need to use a larger bank angle while performing a wing-down cross-controlled sideslip style of crosswind correction on final approach w/ a crosswind, for the same airspeed and the same crosswind component.

Here's a hint: google "electric 3-D model airplane"-- these do all kinds of extreme maneuvers including lots of "knife-edge" flying at low airspeed-- most of the designs have flat-sided fuselages.

@quietflyer I don't understand what you are trying to say in the comment. Could post an answer to my question? (something that might be obvious for you, might take a little bit more to understand for others like me)

A rectangular 3D shape will have a higher coefficient of drag than a cylindrical shape.
So, yes, it will be more sensitive to a change in relative wind.
However, using a "slab side" can allow for a smaller vertical stabilizer if excessive directional stability is encountered.


text:
Has there ever been a transfer of occupants from one aircraft to another while airborne?
Similar to the mechanism used in aircraft tankers (picture below), has there ever been a transfer of occupants from one aircraft to another using some sort of "air bridge"?

Crazy idea: How cool it would be if you could make a connection from a flight to another while airborne. Imagine all the benefits for both airlines and passengers(time saved, airport fees, etc)
I think it would need to be something that when connected would make both aircraft a "single aircraft"(picture below) (to avoid stuff like turbulence), yet a the same time very easy/safe to couple and decouple.

NASA's 747 carrying Space Shuttle. June 2, 2009

Harrison Ford as the US President vibes increasing! get off my plane!!

Barnstormers are reported to have done this.

Anything goes wrong while you're in the middle of that "bridge", you are dead-er than dead! Thanks, but I'd rather connect in Atlanta.

"Imagine all the benefits for both airlines and passengers" yep, especially the two airplane crashing into each other and some passenger missing the bridge and flying away without parachute... WAIT, YOU FORGOT YOUR TROLLEY!!!

ohh come one don't be that cruel....and I bet the FAA certification process would be super easy and quick

Pretty sure the Shuttle wasn't intended to mate up in flight (with the glider having to join up on the jet -- added degree of difficulty there).  Nor any tunnel to connect the two through the orbiter's heat shield.

@RalphJ I really just meant something like it, I know it wasn't intended for that lol. But yeah, I admit it, the idea is just too crazy, I was just passing trough a moment of excitement about this idea. My common senses and reasoning were gone.

see the film Executive Decision :-)

@AaronF indeed, I totally forgot that film.

these folks are prepping it ~ https://www.youtube.com/watch?v=Qh06wlg9RmU

Pretty sure Redbull have moved people from plane to plane - but more likely using those flying squirrel suits than something as sedate and sane sounding (ha!) as a "bridge".

Oh wow. I tried to imagine all the benefits, and came up with none. Disadvatages however were plenty.

One of the Airport movies did this.  Pilots are out of it, and the stewardess is in the cockpit.  They try to transfer a pilot or two though the open cockpit.  Think it was 50/50.

I must admit, I had no idea if the "wire thing" in the Air Force One movie was completely fictional, or perhaps some idea that "special forces" or whatever were actually trying out, or perhaps the air force had experimented with or such. I guess then, it was a totally fictional "Boy's Own" idea. Perhaps someone here knows for sure!

Of course there has! No air bridge involved, however.

This picture shows one of several such performances made for movies or at airshows in the 1920s. The earliest I could find was done by Jim Hester in 1920 for the movie Go Get It.
From the Online Archives of California:

James Harvey Hester was a Stunt Flyer who was associated with the famous Hollywood Black Cats. He served in the USAAS at Kelly Field, TX briefly during WWI then returned to Venice. He was a test and stunt pilot in the southern California area between 1919 and 1925

Follow the link to the San Diego Air & Space Museum collection for more, and treasures like these:

The 13 Black Cats charged one hundred dollars for an ordinary plane-change. It cost five hundred dollars to make a change made from an upside-down aircraft to one flying right side up. A crowd thrilling addition was a faked accident with the apparent victim falling off the aircraft and tumbling about four hundred feet before a thin cable (invisible to the audience) suddenly opened a hidden parachute, to the gasped relief of the audience.

Ahhh... the days before OSHA and Health and Safety.

X-1 pilots took off in the mothership B-29 and transferred to the rocket plane in the air.

At 12,000 feet Yeager, with Ridley behind him, crawled through the hatch to the unpressurized bomb bay. The air temperature was well below zero, and the airstream howled in the confined space. Clad only in a flight suit and leather jacket, Yeager stepped onto the ladder fitted to the right side of the bomb bay, then wormed his way into the X-1’s hatch outside the B-29. Ridley remained on the ladder as the X-1 door was lowered by another crewman. He helped Yeager fit it into place.

https://www.historynet.com/bell-x-1-dropping-the-orange-beast/
An addition to show the ingress setup:
This shows the X-1 tucked under the B-29. The combo was launched hatch-off. You can see the big square hole in the side of the X-1.

This is looking forward and up into the bomb bay with the X-1 not present. The highlighted structure is the retractable ladder. Note it is closed in on three sides and has a floor, the X-1 outer mold line would close off the remaining side when the ladder was extended.

Here's a pilot (Goodlin) transferring from the B-29 to the X-1. The ladder is behind him and the X-1 canopy is visible in front of him.

All photos from Bell X-1 Variants by Guenther and Miller.

I came here to say this. You've already said it, 13 hours ago :-) .

This now sounds like one of the most interesting parts of the X-1 test and even from the article I don't fully understand how they did it.  It sounds like they had two people hanging on a ladder below a flying B-29 who remove, hope not to drop, and then reinstall a door plug in the X-1--and one of those people had broken ribs and went on to fly it.

@ErinAnne I'm flipping through the Aerofax Bell X-1 book and they don't have a great diagram or picture of the ingress setup. But yeah, you described it pretty well. The retractable ladder had a kind of box around three sides of it and a floor, so they weren't totally out in the breeze. I'll add in the best pictures I could find.

amazing. I probably should've asked that as its own question, but the X-1 ladder is now one of the best interface adapters I've seen in my life.

The Red Bull plane swap counts - jumping from one plane to another whilst in free-fall. One person was successful, the other plane went out of control and crashed. The FAA wasn't happy about it...

Well over 20 years ago there was an IMAX movie called "Flyers" that featured a mid-air rescue of a fallen wing walker who had no parachute, but I can't remember whether the rescue plane was the one he/she fell off of (which obviously wouldn't count), or a different one!  Clarification-- this was a fictional story.  What mid-air transfers had to actually be perfomed to get the footage of interest, I have no idea.

Fascinating.  Re the linked video-- they got at least one thing wrong, those were obviously not single-seat planes.

This successful Red Bull stunt would have also counted if the wingsuit flyers had started from a second plane rather than BASE jumping from a mountain into a plane. https://www.youtube.com/watch?v=YL9sNrOlK-I

Mentour AKA Petter covered it (on the "Mentour Now!" channel). Published 2022-05-05. It was about the same time as the Trevor Jacob stunt (within a few months).

What came to mind was a few military projects, although this list is not exhaustive.  Unfortunately the "easy/safe to couple and decouple" was generally a problem. Also note that you not only have to transfer the passenger, but also their baggage.
In the 1930's there were the airships USS Akron and USS Macon which were capable of carrying, launching, and recovering fighters while in the air.
All pictures are from Wikipedia.

The second is the XF-85 Goblin (Note: The plan was to hook up to a B-36, but testing was done with a modified B-29). From Wikipedia:

Two main reasons contributed to the cancellation. The XF-85's deficiencies revealed in flight testing included a lackluster performance in relation to contemporary jet fighters, and the high demands on pilot skill experienced during docking revealed a critical shortcoming that was never fully corrected.

The third one is the related FICON project using a B-36 and F-84. The pilot was able to leave the F-84 while attached to the B-36, but again connecting proved difficult (again quoting Wikipedia):

Subsequent test flights demonstrated the FICON concept was indeed "tactically sound", but its operational implementation was difficult. A total of 10 GRB-36Ds and 25 RF-84Ks were built and saw limited service in 1955–56. Hookups with the carrier aircraft were challenging for the experienced test pilots under ideal conditions. In combat or in adverse weather, and by less-experienced pilots, they proved difficult, and several RF-84Ks were damaged attempting it.

{ Poorly sourced info FYI: }
https://www.airliners.net/forum/viewtopic.php?t=1024005
This bloke claims it has been done a couple times,
"There have been a few aircraft to aircraft transfers done in the real world..."
And following the links other blokes claim it was actually done for real (not effects), with a rope in the Cliffhanger movie.
Other reports claim that he did not actually complete the transfer, while filming.
Unfortunately you can google numerous conflicting stories about that stunt.


text:
Should ATC have souls, fuel, and cargo info before the emergency?
We know how stressful and how fast a situation can become fatal. One of the things that bothers me is when a pilot declares an emergency and I hear ATC asking information they should have already (souls on board, fuel/endurance, dangerous cargo, etc.) when all this info could be available in the flight plan already.
Even on a simple VFR flight without filing a flight plan this info should be automatically filed by ATC if/when pilot does the initial clearance call, something like this:
Miami ground
Cessna 48LG
parked GA ramp
with Charlie
VFR northbound 3,000
souls 2, fuel(endurance)3, no cargo
This information will already be with ATC so in case of emergency they ask the least number of questions possible, and free up the pilot from distractions and more stress.
Does something like this should be implemented so that we have more proactive than reactive response to an emergency?

“Do you think…” is asking for opinions, and the Stack Exchange format is about getting factual answers, rather than discussing what people think about some topic or hypothetical.

Your suggestion sounds unwieldy. If the aircraft (in your example) declares an emergency in Houston, the Houston ARTCC/TRACON/ATCT would have to get in touch with MIA ATCT and ask them to review the audio from when the pilot called for his/her clearance. This information is not available to the controller at the sector in Houston. Regardless of what the pilot told MIA GC, FOB is always going to be a dynamic figure due to changes in routing, cruising altitude, and wind aloft.

As far as souls and cargo, in theory ATC will already have that if there is a flight plan or initial clearance. However:

ATC may not be able to get that information instantaneously - in fact likely only if that particular controller/center is already working with that particular flight.
VFR general aviation (the Cessna example in the question) may have taken off from a small airport with no clearance required and no tower.
In at least some areas, you could have military aircraft seeking assistance in an emergency from civilian ATC or vice versa. Even if each system has relatively complete information about their usual aircraft, they may not have access (particularly civilian ATC for military aircraft) to the "other" system.

But as far as fuel/endurance, ATC will have no idea with the possible exception of a flight that has a problem very shortly after takeoff. If a plane is flying from New York to Los Angeles and has a problem in the midwest, it should have enough fuel to make it the rest of the way to Los Angeles, and therefore to any airport within perhaps 1,000 miles. But that doesn't account for:

Whatever caused the emergency in the first place, particularly something like a fuel leak
Circumstances that were initially under control but which affected fuel consumption in an unusual way - e.g., landing gear not retracted
Unexpected routing due to weather conditions so that the plane has been in the air much longer than it normally would be at this point in the trip

and I am sure many other factors. On the other hand, the pilot will have this information at his/her fingertips and can report it quickly to ATC.

that's a good point about airports without tower

It's also the case that, apart from endurance, knowing these values is not really necessary to respond to the emergency. Hazmat and fuel in pounds are used to know how big of a "boom" to expect, but if you don't know them, you just assume the worst. Souls on board is used to avoid sending firefighters into danger if you already know everybody is out of the plane, but in the worst case, you just have to send someone in, only to find the plane empty.

It is also not entirely impossible to lose souls mid-flight.


text:
What's the efficiency between the duct and the fan blade?
I've heard many times that the smaller the gap between the fan blade and the duct, the better the efficiency/thrust is.
Is there a formula or graph available to see how much efficiency is lost as you increase the distance from the fan blade to the duct?

The answers here might help.

You may look at figure 10 - variations in efﬁciency and leakage with increased clearance, in this document.

Even for just a simple propulsive fan it'll be hard to find one formula incorporating the many practical input variables: blade radius, blade count, blade twist, rpm, airspeed, air density, rotor position in duct, duct narrowing, etc.  I find only measurements and simulations of particular families of these, e.g.
Performance Investigation of Ducted Aerodynamic Propulsors, Bi et al, SMP 2009,
whose conclusion, supported by measurements shown in Fig. 16 (for the same thrust, a gap of 1% to 3% wastes about 10% more power than zero gap), dares to claim nothing more rigorous than:

Propulsor efficiency is insensitive to blade tip
clearance when the tip gap is between 1%R and
3%R. However, as the tip clearance approaches
zero, propulsor efficiency can be quite sensitive
to gap size.


text:
What to do when copilot and captain have a contradiction in a critical situation?
There have been multiple accidents where there is conflict of thinking inside the cockpit between the captain and co-pilot which have lead to unfortunate outcomes due to the critical phase of the flight at which the conflict has happened(i.e. in landing/takeoff or in something like in a low altitude warning flying in IMC).
Watching the documentaries of these accidents, I see a repetitive pattern in particular, and is that usually the copilot was right in the thinking but due to seniority of the captain mixed with the stressful situation the copilot is "ignored" and the captain takes the wrong decision leading to an unfortunate outcome.
What's the best thing to do in a situation like this?
Are there any companies that have some procedures written for this?
Have you experienced something like this and were you able to get out of it without any incident?
Is there something written from the FAA/EASA/ICAO regarding this conflict resolution and specifically on critical time situation like this where a quick action is needed?

Probable duplicates (not an exhaustive list): https://aviation.stackexchange.com/q/100406/7532 and https://aviation.stackexchange.com/q/46779/7532

Just get a book on Crew Resource Management and start reading.


text:
What is this plane flying in overlapping circles pattern doing?
I have seen this Beechcraft Super King Air coming from France near Valenciennes and flying in circular patterns over a zone of Belgium for 2 days in a row now.
What is it doing, some kind of aerial survey ?

Maybe he/she is just building hours, and while doing it, having a nap...

Aerial survey usually looks like this: Why did this aircraft fly in this pattern over Southern Italy? This looks different.

...and more seriously, the pattern is very unefficient for aerial survey. If it was that, the pattern would be regular.

It looks like a glider in a thermal

I would've guessed filming a cycling tournament if it wasn't for the altitude.

Wow, maybe you are right, it corresponds to a cycling race "Tour de Wallonie": Stage 2 and Stage 3. Could it be filming from so high ? Or maybe another purpose...

Geez that's me on a typical cross country!

My guess is if it was circling a major cycle race, it would have equipment on board to serve a a relay station for a TV channel. I've come across this several times in my contry, South Africa.

Meanwhile, in the USA...

How did you get the flight track? (sorry, I realise this is probably common knowledge on here)

@GregWoods See Flightradar24.

They probably turned in the other direction too often, and now they're unwinding the compass.

It's acting as a television broadcast relay for the 2020 Tour de Wallonie cycling race, taking place in Belgium from August 16 through August 19.

The flight paths you posted correspond roughly to the race routes for stage 2 (August 17, Frasnes-lez-Anvaing to Wavre) and stage 3 (August 18, Montzen to Visé).

Here you can see a photo of what one of these broadcast planes looks like, with retractable underbelly antenna:

Thank you - I've come from the bicycles.SE side and had never thought about how those high bandwidth video signals come from the motorbikes to the viewer.

I always assumed they used some short-range radio signals to a stationary TV truck with satellite dishes (or cable internet connection).

@Michael The problem is that the transmitter and receiver would both be at ground level in sometimes hilly terrain, possibly 50 km or more apart, and mobile high-bandwidth links without line-of-sight aren't really possible. But an aerial receiver will have no problem picking up the transmitter.

@TypeIA: Yes, I’m just surprised they are using aerial relays instead of ground relays. I guess it’s just more reliable since you can pretty much always guarantee line of sight.

@Michael Exactly. This race is run in an area with a lot of hills, making ground relays less reliable.

Liking the sly TV in the serial number : )

To me the surprising thing is the double- (or even triple-) relay shown from some of the motorbikes to helicopters, then planes then trucks (which presumably run the satellite uplinks)

@ChrisH The trucks act as field-studios with operators and a director. Various feeds from the mobile units are combined and only a few choice feeds go on the (usually bandwidth limited) satellite uplink. The finish line truck usually handles finish-line interviews, the award ceremony and the live commentary for the various TV stations that will further distribute the live (or recorded) broadcast. The trucks also can process feeds of fixed camera's nearby. That's why you often have them located at summits in mountain races.

@Tonny, yes, the trucks themselves surprise me much less than the illustrated use of  (expensive to run) helicopters as intermediate relays (the 2 marked "RELAY" are drawn without the nose-mounted camera of those marked "WESCAM").  Presumably there's a need for them (that can't be met by the helicopters with cameras, and presumably it's something to do with lines of sight and the fact that the  race  twists and turns though mountainous terrain and gets quite spread out

Aren't helicopters a better choice for the task?

@fraxinus Depends on what's needed for things like endurance, altitude, etc. Airplanes fly much more efficiently than helos, so endurance is usually better. Airplanes (except fighters and VTOL) only require thrust equal to a relatively small percentage of weight, while helos need installed thrust > weight.

@reirab I see. An airplane that carries the same payload as a helicopter is cheaper per unit of time and the excess speed is mitigated by more circling.

@ChrisH My guess for the multiple relays is to deal with obstacle clearance for the signal, especially if it's a particularly hilly or mountainous area. Different helos can hover over individual spots (like valleys) that would be prone to signal blockage even from the airplane and then the airplane can loiter high enough to have LOS to all of those helos and also to ground stations that are in areas not obscured by high nearby terrain. RF is hard. And also finicky. - haha

@reirab, yes, I think you're right.  For the fixed-wing(s) to get LoS to all the ground vehicles would be tricky even at that altitude.  They may also want some redundancy in case of unforeseen events (ground or air) and of course as suggested by your comments to fraxinus, endurance - they can hand-off to a new link that's got plenty of fuel.  I suspect the picture illustrates the broad range of possibilities, and there are some that aren't shown, though maybe the camera helicopters really can't relay

... I've ridden the route of a Tour de France Alpine stage - lines of sight are definitely going to be tricky

@fraxinus: The most efficient way for a helicopter to remain aloft would be to fly in circles.  If one is using an aircraft as a camera platform, hovering in place may sometimes yield better camera footage than flying forward, and that may be worth the extra fuel required to hover, but otherwise flying--whether in an airplane or helicopter--is more efficient.

@Cloud too bad they couldn't get HDTV.. or maybe they did

Wooo! That's the first time I see so many upvotes in less than a week on aviation.SE. Congratulation (I think you deserve it)

@ManuH Surprised the heck out of me too. It's been on the HNQ for a few days now. I think it's a (completely innocently) click-baity question title combined with a surprising and fun explanation. If it gets people excited about aviation in any form then I think that's fantastic!


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Is there an abnormal condition that could have caused this fatal accident involving a stall?
In 2009, a Grob 103 glider stalled and crashed at Richmond Field, Michigan, killing the passenger but not the pilot. (NTSB accident report: CEN09LA353)
The accident occurred after a failed winch launch; during the winch launch, the tow cable broke while the glider was about 400 feet AGL. The pilot correctly decided to turn around and return to the airport.
Here's what happened next, according to a statement the pilot later gave:

I could feel in the controls that something was not right and the glider was not responding in the manner that I am accustomed. There were none of the signs of a stall and the glider did not behave like it has any time that I have practiced stalls. Before I could determine the cause or take any action, the nose abruptly dropped and we dove toward the intended runway.

The NTSB report about the accident states that the probable cause of the accident was simply the pilot's failure to maintain adequate airspeed, resulting in a stall. Judging by this, the NTSB didn't seem to put much stock in the pilot's report that "something was not right".
Suppose that we take the pilot at their word, however. Is there any type of abnormal condition that might have caused a "feeling in the controls that something is not right", and which could cause the nose to drop with "none of the signs of a stall" occurring beforehand?

Please, If possible try to find out if PIC manged to detach the broken cable

@jean I could ask the pilot if they pulled the release, but do you think that's a good idea?

As much as I'd like to find out if the pilot managed to release the broken cable, I'm not aware of a reasonable way to try to find that out. If you think I should try to find that out, please suggest a way I can do so.

Not saying that that's actually what happened here, but a flight-control failure could generate all the symptoms described.

Possibly a Center of Gravity beyond the aft limit could do it, but with 2 adults on board I don't think that's likely unless the person up front was really small and the PIC failed to load ballast to bring the front seat weight up to the minimum.  The NTSB report doesn't say anything about loading so that seems to be a non-issue and there were no other anomalies with the airplane that they could find.  Possibly really bad bug contamination on the leading edges could also affect the stall behaviour and maybe that could've been a factor the investigator overlooked.  Pretty unusual to see gliders with bugs allowed to accumulate that badly, however.
One of the problems with winch launches is when a cable breaks at 400 ft like that, you are in the worst possible place to be, directly over the middle of the runway.  There is no way to get aligned with a runway to land without a fair bit of maneuvering and turning, and you're high enough that landing more directly toward an off-airport field is out of the question, since 400 feet is a lot of altitude to play with in a 35:1 glider, so psychologically the tendency is to be hell bent on landing on the grass directly below you one way or another.  With that kind of unpleasant surprise with the stress level dialed up, it's likely the pilot simply did not perceive the pre-stall behaviour while concentrating on getting lined up.
In gliders the pre-stall cues can be fairly subtle by power plane standards, obvious enough during deliberate practice but easy to miss when mentally loaded up with a life and death do-it-now task. So if I was going to bet a large sum of money on a likely cause, I'd go with the pilot stalling and spinning an otherwise normal glider from failure to maintain flying speed while maneuvering, regardless of what his recollection is.


text:
what's the procedure if you can't establish communication with tower before landing under weather minimums IFR approach?
If for whatever reason(i.e. radio malfunction) you can't establish communication with tower before landing an IFR approach, what is the procedure to follow on that situation?

Gabe I voted to keep your question closed after your edit, because "busy towered airfield" in the other question implies a possibility for IFR conditions. In addition if it was reopened, it might be a duplicate of  Navigate to the final approach course after radio failure under IFR which has a very detailed answer including squawking 7600.


text:
Do all International airports need to be certified by ICAO?
Amidst the recent accident of Jeju Air Flight 2216 in South Korea, and many experts mentioning that there was a bad construction design of the embankment holding the ILS array, I think I've heard long time ago (if I'm not wrong) that international airports have to be certified by ICAO or something like that, so I wonder if it was the case at Muan Airport.
So, beyond any factors involved for this particular accident, simply my only question is if ICAO needs to certify the construction of all International Airports (or the company that builds the airport) in any way shape or form.

ICAO does not directly certify the construction or operation of international airports.
Instead they provide Standards and Recommended Practices (SARPs) through Annex 14 of the Chicago Convention, which covers "Aerodromes."
These standards set out the requirements for the design, construction, and operation of international airports.
But it's up to the country's aviation authority to make sure if their airports are following these standards
In this document, it has been written

1.2.5  RECOMMENDATION
Those portions of the strip immediately beyond the limits of the runway should be so prepared or constructed as to minimize hazards, arising from differences in load bearing capacity, to an aircraft running off the runway.

In addition, 1.2.4 regulates the longitudinal and transverse slopes of strips beyond the runway to ensure safe conditions for aircraft that might veer off the runway.
So there are standards set by ICAO, ideally they should be followed, they aren't always followed though.

Do all International airports need to be certified by ICAO?

They have to be certified
They are certified by local authorities.

All international airports in an ICAO State member have to be locally certified, according to all applicable ICAO standards.

ICAO and Civil Aviation Convention
ICAO:

Is a UN agency which role is to facilitate international civil flights, by creating agreed standards and recommendations.

Is made of aviation agency representatives from all State members, as well as representatives of other organizations like meteorology (WMO) and radiocommunications (ITU) international agencies.

Is  not a certification agency. It's much more comparable to a standardization organization like ISO.

ICAO State members have signed a Convention and its Annexes which contain both standards and recommendations. State members have to implement all standards, unless impossible to do so (Annex 2, Rules of the Air).
Recommendations are only suggestions for State members. In ICAO Annexes, recommendations are explicitly identified by "recommendation" and are in italic type.
ICAO Convention and its Annexes are treaties committing States, not citizens. Standards and recommendations must be implemented in local regulations to become applicable to citizens in a country.
The mandatory way to inform the international aviation community about local aviation regulations in use is to publish them in the aeronautical information publication (AIP).
Each State member publishes its own AIP.
General case
Aerodrome certification is described in Annex 14 and details are given in Doc 9774:

1.4.1 States shall certify aerodromes used for international operations in accordance with the specifications contained in this Annex as well as other relevant ICAO specifications through an appropriate regulatory framework.

1.4.2 Recommendation.— States should certify aerodromes open to public use in accordance with these specifications as well as other relevant ICAO specifications through an appropriate regulatory framework

Note the difference: 1.4.1 is a standard, international airport must be certified. 1.4.2 is a recommendation, other airports open to public use should be certified.
Korea case
In Korea AIP, at section AD 1.1:

1.2 Applicable ICAO documents: ICAO Standards and Recommended Practices contained in the ANNEX 14 are applied to the maximum extent possible.
ANNEX 14 - Aerodromes Volume I & II
Doc 9157 - Aerodrome Design Manual(Part 1 to 6)
Doc 9137 - Airport Services Manual(Part 1 to 9)

As usual in all AIP, the GEN 1.7 section is used to indicate if the local law ignores or modifies some ICAO standard, with an explanation of the difference. This is to comply with by Article 38 of the Convention.
This section is sorted by ICAO Annex number. Certification of aerodromes is part of Annex 14 (aerodromes):

1.0.1 The Republic of Korea defines "Aerodrome Certificate" in ICAO Annex 14 as "Airport Operating Certificate". Airport Operating Certificate means a certificate, issued by Ministry of Land, Infrastructure and Transport.

1.4.2 The Republic of Korea certifies airports used for international operations mandatorily and the certification will be expanded to other airports open to public use.

Airports certification statuses are listed at section AD 1.5 (Muam was certified in Nov. 2007).

References:

ICAO Convention and annexes
Annex 14, Volume I, Aerodrome Design and Operations (pdf)
Doc 9774, Manual on Certification of Aerodromes (pdf)
Doc 10066, Aeronautical Information Management (pdf)


text:
Which US State has the most General Aviation aircraft manufacturers?
Curious if there is a specific geolocation manufacturers prefer for building their aircraft knowing that it is a multifactor decision (testing, permits, cost, labor, weather, etc)
I wonder if there is a US State that has the most General Aviation aircraft manufacturers?

It's hard to compare "most." Textron has a huge operation in Wichita but it's one company, while Epic is a building in an airstrip in Oregon.

@user71659 I see your point, I'm just interested knowing by total number of manufacturer companies, doesn't matter if is small or big. The essence of the question is to find out if there is something that attracts manufacturers more to a specific state or it is just spread/random.

It is historical.  Wichita was the home to Beech, Cessna, Stearman, Travel Air, and Learjet.  Boeing followed with a large presence.  Those companies have closed, merged, been bought, etc. leaving mostly Textron (Cessna and Hawker Beechcraft) and Spirit (a Boeing spinoff that is being re-acquired by Boeing).  The other big location for many companies is Los Angeles -- Douglas, Northrop, Lockheed, Hughes, North American (briefly in MD) were all LA centered.

Today, Lockheed employs people in every congressional district.  McDonnell (St. Louis) merged with Douglas, which merged with Boeing.  North American Aviation became Rockwell and is now part of Boeing.  The year-round good flying weather is a good reason for aerospace companies to locate in Southern California.

@RobMcDonald The question asks for GA. Boeing, Lockheed, Spirit aren't GA by any stretch. Those have work-share considerations, GA doesn't.

There is no reason to expect it would be spread at random but it's not to say that there is some objective pre-existing characteristics that attracts manufacturers to a state. It's a common thing for many industries, there is quite a bit of literature (which I do not know very well) on that in economics or policy circles, see Wikipedia.

Don't know the answer but I'll bet Florida's in the top 5.


text:
Will we ever see a single-engine airliner?
Given the trend in the industry to move towards aircraft with two engines, could it ever occur that we see an aircraft manufacturer develop an airliner with just one?
I'm suspecting the answer is no, given the redundancy offered by a twin engine configuration (e.g. if the independent probability of engine failure is one chance in a thousand, the probability of dual engine failure is one in a million.). I know the Virgin Global Flyer used one engine (https://en.wikipedia.org/wiki/Virgin_Atlantic_GlobalFlyer) presumably because the risk of engine failure was acceptable given the task in question.
However, if someone were to manufacture an engine with a probability of failure below, say one in 100 million, could this configuration make sense from an economic perspective?

I replaced your references to "commercial" with "airliner" because commercial operations with single engine aircraft (C208, PC-12) are already ubiquitous, and the body of your question explicitly and implicitly referred instead to airline operations.

Great, thank you for the correction.

Welcome to the site @TerryLennox, and thanks for the question. Unfortunately this question at the moment is opinion based, and is too broad. Could it happen? Sure, why not, if you had an engine that reliable I'm sure it would be used. Will it happen nobody can truly say.

In Soviet times, Aeroflot operated a large number of single-engine Antonov biplanes. If Wikipedia is to be believed, ex-Aeroflot Antonovs are still transporting passengers in Asia and South America...  Many ex-Aeroflot An-2s have since found work with regional airliners across Africa, Central and South America, Cuba and southeast Asia. https://en.wikipedia.org/wiki/Antonov_An-2#Civil_aviation

@J Walters: How do you define "airliner", though?  If it's "an airplane used in regularly-scheduled passenger operations", then those C208, PC-12s, and similar single-engine planes are airliners.

Not necessarily. That is a difficult question to answer. I've asked here on this site for a good definition of airline, and haven't received a definitive answer. To my knowledge the "airlines" operating the single engine turboprops are actually operating under 135 rules, not 121 rules. Those pilots are not required to have Airline Transport Pilot (ATP) licences. I fly business jets under 135 rules as for a charter company; I am required to have a my ATP. Typically 121 operators are considered airlines. It's not an easy question to answer as there are no apparent official definitions.

of course commercial PASSENGER operations with single engine aircraft are illegal in many countries (certainly in EASA countries). And that alone is a big reason why there are no single engine airliners (not even regionals) any longer (they used to exist, in the early days, think early Fokker designs).

There are two major problems I see.

Even if you have an incredibly reliable engine how do you prove it is incredibly reliable. I can't seem to find figures for the target IFSD rate for the current higher ETOPs levels, but I find figures for early ETOPs of one per one hundred thousand hours. Lets say you improve that to one per billion hours, how exactly do you demonstrate it's that low? fly for a billion hours? Thats a hundred planes flying for a thousand years. This is why redundancy is the route taken for many safety critical systems, you can argue that the individual components are merely very reliable and then argue that the chance of two of them failing at once is extremely low
Where do you put the engine? If you have a single engine you want it on the centerline. That is not such a problem for props or low bypass turbofans, but it's difficult for high bypass turbofans.

Because of these two factors I doubt we will see airliners move to a single engine configuration unless we see fundamental changes in airliner design and regulation.

Thanks for the answer, it's really interesting of course that it's not easy to site a high-bypass turbofan on the centreline, I know that trijet aircraft did this, but it caused a quite a few issues as far as I understand.

In the era when trijets were a thing engines had much lower bypass ratios than they do today, so their inlets were much smaller.

That makes sense, I can't imagine mounting a GE90 on the centreline!

What about like the old DC's? Mount a turbofan up on the tail?


text:
Can PPL hours be from multiple countries (Europe, UK)?
If you have some PPL hours from various European countries, such as France, Spain, Portugal, Greece - do these count towards the minimum 40 hours to take the PPL GST in the UK?

Great question, aviation regulations post-brexit are a complete mess. Really hard to find the actual answer.

@Jamiec Why do the CAA not make this information clearer I wonder.

This question likely falls under the domain of "interpretation of regulations spaghetti." Find a flight training outfit in your area and ask.

@mins Just like US law more like!

If you have PPL hours from countries such as the ones you mentioned they can count for the minimum 40 hours you need for the PPL GST test in the UK as long as they were completed under the standards of an ICAO-compliant training program. The CAA recognizes flight training from ICAO members including all the countries you mentioned. There are some additional requirements you will need to meet such as a Valid UK medical certificate class 1(Or 2 depending on your plans for future flight operations) and some other requirements you can find in my listed sources.
SOUCES:

How to validate your ICAO third country license
Private pilot license for airplanes
Third Country License conversion requirements from 1 January 2023.

@Jamiec is this correct? Asking you as I know you are close to the CAA..

@Cloud I'm about as far from the CAA as a person could be. As I've explained to you before :) All 3 of those links are to pages on the UK CAA website, so that's about as authoritative as you can get for UK Aviation regulation.


text:
How are fly-by-wire airliners controlled in case of complete electrical failure?
In this comment, it is postulated that even fly-by-wire aircraft (Airbus) are demonstrated to fly without any electrical systems:

All Airbus aircraft are demonstrated controllable with complete electrical failure. They would be pretty difficult to land if the electronics didn't at least partially recover (because the backup only allows controlling pitch and yaw and roll only via yaw-roll stability), but it would still be possible. [...] Jan Hudec Dec 21 '14 at 21:38

My question, assuming complete electrical failure, how exactly is this done? What controls have mechanical linkage (pitch trim? engines? flaps/slats?) Would it be possible, in theory, to land the plane in such a way that some passengers could walk away? (Perfect weather, miles of flat tarmac runways everywhere, cinematic pilot capabilities)

For the complete electrical failure in the aircraft, the following systems have to fail:

The onboard power generation system, usually a synchronous generator has to fail in all the engines.
The APU (Auxiliary Power Unit) has to fail.
The RAT (Ram Air Turbine) should fail to deploy.
The batteries and static inverters should fail (this won't help in controlling the aircraft, just added for sake of completeness).

The probability of this happening is very very low, and can be discounted. It is more probable that some other system (for e.g, hydraulics) fail before this happening. So far, to the best of my knowledge, no complete power loss has been reported in any fly by wire aircraft.
The reason the Airbus aircrafts are controllable in case of electrical failure is due to the fact that the fly-by-wire system has multiple redundancies that offer layered protection:

Normal Law offers all the protections (like stall, load factor etc). This is the system in operation during normal flights.
Alternate Law offers limited protection including stability, load factor and stall protections
Abnormal Alternate Law limits the load factors and offers yaw damping only
Direct Law is the lowest level of fly-by-wire system and directly transmits the pilot inputs to control surfaces, while still giving stall and load factor warnings
In case all these fail, the system reverts to mechanical backup, where pitch control is achieved through the horizontal stabilizer and lateral control is accomplished using the rudder pedals.

In case of mechanical backup, the system will operate as long as hydraulic power is available. In case of electrical failure, as long as hydraulics are OK, the pilot should be able to control the aircraft.
However, usually, if there is no power, there is no hydraulic pressure (except reservoir, maybe) and the control is lost. In case of the Baghdad DHL aircraft, only hydraulics was lost and power was available.
There are some more points to consider in case of total electrical failure.

In case the control surfaces are moved by electric power (like 787), power loss means loss of control.
Power loss implies that the engine thrust cannot be controlled (of course, the engines won't be operational in that case anyway).
Some fly-by-wire aircrafts are unstable by design. In these cases, any power loss will lead to loss of control and crash.
I'm not sure there is any direct mechanical linkage in civil airliners. The amount of force required to operate such a system would be enormous.

Bottom-line is, in case of complete power failure, the aircraft is as good as dead. One example is a Fairchild Swearingen Metroliner (which was not fly-by-wire), that lost complete electrical power due to a lightning strike. The aircraft entered into a uncontrolled flight, which loaded the aircraft beyond limit, resulting in its disintegration.

The uncontrolled flight was likely a spiral dive due to loss of instrument reference in IMC -- that's the main danger with a total power loss.  Also, the DC-9 family uses servo tab primary controls (the rudder and elevator have hydraulic boost, but it isn't needed all that much), and Boeings from the 707 through the 737 have manual reversion in at least pitch and roll.

Does mechanical backup really require hydraulics?  That doesn't sound very mechanical to me, and in fact I have heard in the past that there is an actual mechanical connection for just this purpose...

I believe the Boeing 737 is the largest airliner to have direct mechanical (ie. cable) linkage for its controls, and even that's indirect: the linkage controls servo tabs which in turn use aerodynamic forces to move the control surfaces.  Still, you can (attempt) to fly a 737 even with complete failure of all power systems.

@Mark -- 737 and DC-9 families, yes.  (many RJs are actually non-reversion, interestingly enough, AFAIK, the ERJ-135/145 are the only reversion capable RJs in common use)

How do these statements line up? In case all these fail, the system reverts to mechanical backup and I'm not sure there is any direct mechanical linkage in civil airliners. The amount of force required to operate such a system would be enormous.?

Which controls have mechanical linkage differs between models.
In A320 the pitch trim and rudder have mechanical linkage. There is no mechanical backup for roll control; roll control is only possible via yaw-roll coupling.
Remember, that mechanical link really means hydraulic. Without hydraulic pressure the aircraft is not controllable. However at least in A320 the RAT drives a hydraulic pump for the blue system directly.
The mechanical backup is meant for the case of total failure of the flight computers rather than complete failure of electrical power, but that is well in line with what the question on which the commend was made asked.
As aerolinas already mentioned, complete electric failure is extremely unlikely with all the backups there are. But then, complete failure of all the flight computers is not much more likely and as far as I can tell never happened in practice.

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